When a certain compound has two or more kinds of crystal forms, these different crystal forms are referred to as crystal polymorphism. It is commonly known that stability varies with each crystal form of crystal polymorphism. For example, Japanese Unexamined Patent Publication (Kokai) No. 62-226980 describes that two kinds of crystal forms of prazosin hydrochloride have different stabilities and exert an influence on the results of long-term storage stability. Also Japanese Unexamined Patent Publication (Kokai) No. 64-71816 describes that a specific crystal form among different crystal forms of buspirone hydrochloride is advantageous in view of retention of specific physical properties during storage or under manufacturing conditions.
In the production of a drug substance for medicine, it is advantageous for the storage stability and control of manufacturing process of the drug substance and pharmaceutical composition to obtain the drug substance in a crystal form.
In case a compound having two or more crystal forms is employed as a medicine, physicochemical properties such as melting point, solubility and stability, and pharmacokinetics such as, absorptivity, distribution, metabolism and excretion vary with each crystal, and thus biological properties such as appearance of drug efficacy vary sometimes. To ensure that the resulting medicine has stable properties described above, it is often required to produce a drug substance having a specific crystal form. Also in the process for production of the drug substance, it is important to precipitate a specific crystal form in the crystallization operation so as to maintain the yield and purification effect.
It is impossible to anticipate the presence of crystal polymorphism by the structure of the compound, and it is considered to be important to find out a crystal form in the development of the medicine.
As described in WO 00/03997 and WO 01/53291, it is known that 4-(1-((4-methylbenzothiophen-3-yl)methyl)benzimidazol-2-ylthio)butanoic acid represented by the following formula (I) has an effect of inhibiting chymase.

However, there is not any description about the crystal or crystal polymorphism in the above references.
Chymase is one of neutral proteinases present in mast cell granules and has a close relation with various vital reactions associated with mast cells. There have been reported various effects, for example, acceleration of degranulation from mast cells, activation of Interleukin-1-β (IL-1β), activation of matrix protease, decomposition of fibronectin and IV type collagen, acceleration of release of Transforming growth factor-β (TGF-β), activation of material P and bathoactive intestinal polypeptide (VIP), effect of conversion from Angiotensin (Ang I) into Ang II, and Endothelin conversion effect. As is apparent from the above description, it is considered that an activity inhibitor against chymase is useful as a preventive and/or a remedy for respiratory tract diseases such as bronchial asthma; inflammatory and/or allergic diseases such as allergic rhinitis, atopic dermatitis, and urticaria; circulatory diseases such as sclerosing vascular lesion, intravascular stricture, peripheral circulatory disturbance, renal insufficiency, and cardiac insufficiency; and bone and/or cartilage metabolism diseases such as rheumatism and osteoarthritis.